mike4, can you elaborate? What do you mean by import?
Opening it? Then you just need to go to File->Open Project or File.
Adding it as subproject to your project? Just copy it near your sources and modify your .pro-file (or add new one with SUBDIRS).

If you simply need to add all files to your project then you can use Add Existing Files option in created project.
If you need to import makefile too then afaik New Project->Other Project->Import Existing Project will help you.